The subject matter of the present invention relates generally to log processing apparatus and, in particular to veneer lathe chargers of the type which rough center the log in a scan position, rotate the log while scanning such log with light or other electromagnetic radiation to determine its optimum yield axis, adjust the position of the charger spindles to align such optimum yield axis in a predetermined transfer position, and transfer the log from such transfer position to the lathe axis. The lathe charger apparatus of the present invention accomplishes such adjustment of the charger spindles over a greater range necessary for logs of larger diameter and enables engagement of the opposite ends of such log by transfer clamp means while the spindles still engage the log, thereby eliminating any need to reclamp the side of the log with rough centering arms after scanning. The lathe charger apparatus of the present invention provides sufficient clearance to enable the transfer clamp means to move from contact with a previous log in the lathe spindle position to the transfer position for engagement with the next log while the charger spindles are still engaged with the ends of such next log. This is made possible by providing directionally limited adjustment of the charger spindles to move the optimum yield axis of the log into the transfer position after scanning to determine such optimum yield axis. This directionally limited adjustment of the log is accomplished by an automatic control means which rotates the log to a different rotational position after scanning to enable the log to be moved through its greatest adjustment in a direction other than toward the transfer clamp means in the transfer position. In addition, the charger spindle support and adjustment means is adapted to move the charger spindle means away from the transfer clamp means a greater distance than toward such clamp means. In this regard a stop means can be employed to prevent the charger spindles from being moved into a position of interference contact with the transfer clamp means as the latter is moved from the lathe spindle position to the transfer position.
The lathe charger apparatus of the present invention is an improvement on my earlier light scanning lathe charger disclosed in U.S. Pat. No. 4,197,888. This earlier lathe charger required that the log be reclamped by the rough centering arms after scanning and the charger scanning spindles disengaged from the ends of the log to provide sufficient clearance for the transfer clamp arms to swing past such spindles and engage the ends of a log. In order to attempt to avoid this need for reclamping of the log by the rough centering arms, a second embodiment is shown in FIG. 11 of such patent employing a special transfer clamp arm with a pivotally mounted clamp end portion operated by a cylinder. However, this solution is complicated and expensive.
In my earlier U.S. patent application Ser. No. 06/154,201, a lathe charger is disclosed which eliminates the need to reclamp the log by the rough centering arms and provides sufficient clearance for the transfer clamp means by locating the charger spindles at a scanning position which is spaced a predetermined distance below the transfer position axis. This enables the transfer clamp arms to move from the lathe spindle position to the transfer position while the log is in the scanning position and thereafter moving the log upward from the scanning position until its optimum yield axis is positioned in alignment with the transfer position axis by adjustment of the charger spindles. Then the transfer clamp means is moved into engagement with the ends of the log and the charger spindles are retracted to provide sufficient clearance for the transfer clamp arms to move from the transfer position back to the lathe axis position. Unfortunately, the maximum adjustment of the position of the charger spindles is somewhat limited in such charger, being only .+-.1.5 inches from the center of an ideal circular cylinder. As a result, large diameter logs requiring more than 1.5 inch adjustment between the rough geometric center and the optimum yield axis, cannot be correctly positioned.
In my earlier U.S. Pat. No. 4,197,888 a lathe charger apparatus is disclosed in which the optimum yield axis of a log is determined by light scanning such log. Light beams are directed past the side of the log through the space between such log and a reference edge to project an image of such space onto photoelectric detectors at longitudinally spaced positions while the log is rotated on charger spindles. The output signals of such detectors are fed to a computer which determines the optimum veneer yield axis of such log. After such scanning, the charger spindles are adjusted horizontally and vertically to position the optimum yield axis of the log at a transfer position axis located at a predetermined position relative to the lathe spindle axis. Transfer clamp arms engage the ends of the log and move such log from the transfer position to the lathe axis. This positioning of the log is accomplished automatically by means of the computer control system shown in FIG. 9 of such patent. A similar computer control system is employed in the present invention to determine the optimum yield axis of the log and to adjust the position of the charger spindles. However, in the present invention the computer is programmed to provide directionally limited adjustment of the charger spindles so that the maximum adjustment of the log is in a direction other than toward the transfer clamp arms when its optimum yield axis is aligned with the transfer position axis.
Other scanning techniques can be employed to determine the optimum yield axis including the light reflection technique shown in U.S. Pat. No. 3,852,579 of Sohn et al. In addition, other electromagnetic radiation other than light can be employed during scanning, such as microwaves. Therefore, the present invention is not limited to light beam scanning of the type shown in U.S. Pat. No. 4,197,888 to determine the optimum yield axis.
As a result of eliminating the need to reclamp the side of the log with the rough centering arms after scanning or to disengage the charge spindles before engagement by the transfer clamp means, the lathe charger apparatus of the present invention is considerably simplified and faster operating. Thus, the rough centering arms can move to receive a new log during scanning rotation of the previous log to determine its optimum yield axis and adjustment of the charger spindles holding the previous log to align such optimum yield axis with the transfer position axis. Also, the transfer clamp arms or other transfer clamp means can return immediately from the lathe axis position back to the transfer position and do not have to wait for reclamping of the next log or disengagement of the charger scanning spindles from such next log before reclamping. Finally, by employing directionally limited adjustment of the charger spindles to align the optimum yield axis of the log in the transfer position a greater range of adjustment is achieved. The result is a faster and more efficient lathe charger operation by an apparatus which is capable of properly adjusting the optimum yield axis of the logs of larger diameter.